Thesis: Elec. E., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 1975 / Includes bibliographical references. / Elec. E. / Elec. E. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science

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In recent years, Light-emitting Diodes (LEDs) have become a promising candidate for backlighting Liquid Crystal Displays [1] (LCDs). Compared with traditional Cold Cathode Fluorescent Lamps (CCFLs) technology, LEDs offer not only better visual quality, but also improved power efficiency. However, to fully utilized LEDs' capability requires dynamic independent control of individual LEDs, which remains as a challenging topic. A FPGA-based hardware system for LED backlight control is proposed in this work. We successfully achieve dynamic adjustment of any individual LED's intensity in each of the three color channels (Red, Green and Blue), in response to a real time incoming video stream. In computing LED intensity, four video content processing algorithms have been implemented and tested, including averaging, histogram equalization, LED zone pattern change detection and non-linear mapping. We also construct two versions of the system. The first employs an embedded processor which performs the above-mentioned algorithms on pre-processed video data; the second embodies the same functionality as the first on fixed hardware logic for better performance and power efficiency. The system servers as the backbone of a consolidated display, which yields better visual quality than common commercial displays, we build in collaboration with a group of researchers from CREOL at UCF.

Yes / A tuneable slotted patch antenna design is presented and verified for use in the DCS, PCS and UMTS bands. The tuning circuit consists of two varactor diodes with some passive components, and is integrated fully with the r radiator patch, with the varactors occupying different locations over the slot. The tuning does not require any further modification to the patch or feed geometry. Good agreement is observed between the predicted and observed impedance bandwidth, return loss, gain and radiation pattern, throughout the range 1.70 GHz-2.05 GHz.

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<p>Superluminescent diodes have become important for various applications, such as for biomedical imagining, due to their broad spectral width and high power.</p><p>This thesis demonstrates two-section superluminescent diodes fabricated using quantum well intermixing with strained Ga_0.75sln_0.25As quantum wells, grown on a GaAs substrate. A 100 nm capping layer of Ga_0.515In_0.485P grown at low temperature and having an excess of phosphorus, was removed from one section of the device to produce a relative bandgap shift between sections after rapid thermal annealing. The devices emitted at a wavelength of ~1μm with 60 nm of spectral width, and up to 38 mW of power at 20°C, depending on the currents applied to each section.</p><p>The combination of the spectral output from the two quantum well intermixed sections resulted in the broad spectral width. Angled facets at 7 ° were used to prevent the device from lasing. Additional power improvements were seen following the thermal anneal when a SiO2 capping layer was used on both sections. Depending on the applied currents, each section required 1.5 V to 3.0 V; and failed at 5.3 V ± 0.5 V.</p> / Thesis / Master of Applied Science (MASc)

The objective of this thesis is to study the dynamic properties of laser diodes and the compensation for the nonlinearities of laser diodes based on the theory of Volterra series. In the first part of this thesis, an analytical expression in Volterra series is discussed to depict the nonlinear distortion of laser diodes up to the third order. The simulation results of this analytical method show that Volterra series model improves the accuracy of the description of the nonlinearity of laser diodes in comparison with small-signal analysis model. In the second part, the p^th-order inverse theory is introduced to compensate the lasers' nonlinear distortion. The compensation scheme is constructed and the simulation of the system is conducted in this thesis. The result shows that the laser nonlinear distortion can be compensated by using this technique. / Thesis / Master of Applied Science (MASc)

Power devices play key roles in the power electronics applications. In order for the power electronics designers to fully utilize the performance advantages of power devices, compact power device models are needed in the circuit simulator (Saber, P-spice, etc.). Therefore, it is very important to get accurate device models. However, there are many challenges due to the development of new power devices with new internal structure and new semiconductor materials (SiC, GaN, etc.). In this dissertation, enhanced power diode model is presented with an improvement in the reverse blocking region. In the current power diode model in the Saber circuit simulator, an empirical approach was used to describe the low-bias reverse blocking region by introducing an effect called "conduction loss," a parameter that causes a linear relationship between the device voltage and current at low bias voltages with no physics meaning. Furthermore, this term is not sufficient to accurately describe the changes to the device characteristics as the junction temperature is varied. In the enhanced model, an analytical temperature dependent model for the reverse blocking characteristics has been developed for Schottky/JBS diodes by including the thermionic-emission mechanism in the low-bias range. The newly derived model equations have been implemented in Saber circuit simulator using MAST language. An automated parameter extraction software package developed for constructing silicon (Si) and silicon carbide (SiC) power diode models, which is called DIode Model Parameter extrACtion Tools (DIMPACT). This software tool extracts the data necessary to establish a library of power diode component models and provides a method for quantitatively comparing between different types of devices and establishing performance metrics for device development. This dissertation also presents a new Saber-compatible approach for modeling the inter-electrode capacitances of the Si CoolMOSTM transistor. This new approach accurately describes all three inter-electrode capacitances (i.e., gate-drain, gate-source, and drain-source capacitances) for the full operating range of the device. The model is derived using the actual charge distribution within the device rather than assuming a lumped charge or one-dimensional charge distribution. The comparison between the simulated data with the measured results validates the accuracy of the new physical model. / Ph. D.

An experiment was conducted to evaluate the potential of producing dwarf tomatoes (Solanum lycopersicum L.) in an indoor vertical system. Cultivars 'Micro Tom', 'Jochalos', and 'Venus' were grown under the three daily light integral (DLI) levels of 16.9, 22.7, and 27.9 mol·m-2·day-1. Cultivar had an effect on height, with Jochalos being the tallest. Plants grown under 27.9 mol·m-2·day-1 were the shortest. The time of first flower was affected by cultivar, appearing earliest in Micro Tom. Regarding DLI, the first flower was earliest in plants under 22.7 and 27.9 mol·m-2·day-1. The time of first harvest was only affected by cultivar, in which Micro Tom was earliest. There was an interaction effect for the total and marketable fruit count harvested. Micro Tom had the highest overall number of fruits harvested amongst cultivars, and Micro Tom grown under 22.7 and 27.9 mol·m-2·day-1 had more total and marketable fruit counts than those grown under 16.9 mol·m-2·day-1. There was no interaction effect for fruit weight harvested. The effect of cultivar differed between the total and marketable fruit weights harvested, but Jochalos produced the highest weights in both. The effect of DLI was the same for total and marketable fruit weights harvested, with plants under 22.7 and 27.9 mol·m-2·day-1 having the highest weights. Cultivar had an effect on fruit Brix, with Micro Tom fruit having the lowest Brix and Jochalos fruit having the highest Brix. The effect of DLI resulted in fruits produced by plants under 27.9 mol·m-2·day-1 having the highest Brix and fruits produced by plants under 16.9 mol·m-2·day-1 having the lowest. Based on these results, there is potential for dwarf tomatoes to be grown in vertical farm systems. / Master of Science in Life Sciences / An experiment was conducted to evaluate the potential of producing dwarf tomatoes (Solanum lycopersicum L.) in an indoor vertical system. Cultivars 'Micro Tom', 'Jochalos', and 'Venus' were grown under the three daily light integral (DLI) levels of 16.9, 22.7, and 27.9 mol·m-2·day-1. Cultivar had an effect on height, with Jochalos being the tallest. For DLI, all plants grown under 27.9 mol·m-2·day-1 were the shortest. The time of first flower was affected by cultivar, appearing earliest in Micro Tom. Regarding DLI, the first flower was earliest in plants under the higher DLIs. The time of first harvest was only affected by cultivar, in which Micro Tom was earliest. There was an interaction effect for the total and marketable fruit count harvested. Micro Tom had the highest overall number of fruits harvested under the highest DLIs. There was no interaction effect for fruit weight harvested. In cultivars, Jochalos produced the highest weights for both total and marketable fruits. Plants under 22.7 and 27.9 mol·m-2·day-1 had the highest weights for total and marketable fruits harvested. Cultivar had an effect on fruit Brix, with Micro Tom fruit having the lowest Brix and Jochalos fruit having the highest. Uninfluenced by cultivar, fruits produced by plants under 27.9 mol·m-2·day-1 had the highest Brix, while those under 16.9 mol·m-2·day-1 had the lowest. Based on these results, there is potential for dwarf tomatoes to be grown in vertical farm systems.